Two years ago to the snap, the international sporting community was agog over the 49ers’ fortune.

Blessed with a little luck and plenty of scouting brilliance, the 49ers had on their 53-man roster a player who was so dynamic, so ripe with dazzling promise, his presence alone caused mouths to drop all across the planet.

Jarryd Hayne, a walk-on running back/kick returner from Sydney, was an undrafted free agent on the 2015 49ers squad. A star in his prime with the National Rugby League, arguably Australia’s toughest footy code, Hayne’s knowledge of the NFL was limited to mostly what he learned from playing “Madden NFL” video games. Undaunted and encouraged by American scouts drooling over his size and speed, Hayne chucked it all in his native country and gave the gridiron a go.

It was some story: Hayne navigated American football like a croc in salt water, shedding tackles with dazzling moves and boomeranging off blockers during the preseason...